1. Field of Invention
This invention relates to optics. Specifically, the present invention relates to shaping optics for diode light sheets.
2. Description of the Related Art
Lasers are used in high pulse energy applications such as weapons, radar and ranging. To be most efficient, the pump density needs to be high, and the distribution should be tailorable as well as energetic. However, current laser diodes are manufactured with a minimum internal spacing dictated by cooling requirements for each diode. With directly coupled systems where the diode array is placed as close to laser medium as possible, this spacing dictates pump density, and is not necessarily ideal for laser gain media such as Nd:YAG or Nd:YLF.
Diodes alone produce a limited fixed distribution profile. Conventional lenses, typically standard spherical optics, may be added to produce limited shaping of the profile. A traditional diode-to-slab coupling optic has a constant radius spherical surface. Due to the constant curvature of the spherical surface, such a cylinder lens cannot concentrate the light sheet output from a micro-lensed diode bar stack to produce a gaussian-like deposition profile within a laser gain medium such as Nd:YAG or Nd:YLF. Prior art lenses do not allow the creation of an arbitrary pump light distribution from the multiple light sheet output of micro-lensed diode arrays of any pitch spacing.
Thus, a need remains in the art for an optic which can channel the multiple light sheet output from a diode stack of arbitrary pitch and diode bar number into a desired customized pump light deposition profile within a laser gain medium.
The need in the art is addressed by the present invention which provides a Fresnel cylinder lens having a plurality of facets which channel multiple light sheet output from a diode stack having arbitrary pitch and diode bar number into a gaussian pump light deposition profile within a laser gain medium.
In a specific embodiment, the lens is formed of fused silica or BK7 glass covered with broad angle anti-reflection coating, and the vertical extent of the facets is matched to the pitch spacing of the diode.